1. Field of the Invention
The present invention pertains to the art of cooking appliances and, more particularly, to a cooking appliance including a sensor for detecting the presence of a cooling airflow.
2. Discussion of the Prior Art
In general, providing a cooling airflow system in a cooking appliance is known. It is also known to provide a sensor or monitor to detect the presence of an airflow in the cooling system. The most common method used to detect the airflow includes providing a sail switch in an airflow path contained within the cooling system. A sail switch is actually a micro-switch having a large vane secured to a switch arm. With this arrangement, the cooling airflow impinges upon the vane, causing the switch arm to change position. This change of position provides a controller with information regarding the existence of the cooling airflow.
While this method enjoys wide use in the cooking appliance industry, sail switches are rather prone to failure. As a matter of fact, sail switches are somewhat delicate and, consequently, have multiple failure modes. For example, sail switches are subject to mechanical misalignment, shipping and other mechanical abuse and, finally, poor calibration. Each of the above examples would lead to a failure in the field. As modern appliances include a wide array of electronic components, undetected cooling system failure could result in costly damage to the appliance. Moreover, as safety standards set by regulatory and other agencies require that an oven be shut down in the event of cooling system failure, it is important to provide a monitor or sensor possessing a high degree of reliability.
Another method used to monitor for the cooling airflow includes providing a pressure sensor within the airflow path. This method primarily relates to commercial ovens where temperatures are high, the oven is operated for a prolonged period and a high pressure cooling airflow is provided to maintain cooler temperatures within control compartments of the oven. While appropriate for higher pressure airflows, such systems do not lend themselves to incorporation into residential ovens where airflows are provided at much lower pressure levels.
Therefore, despite the presence of these airflow monitoring systems in the prior art, still there exists a need for an improved airflow sensor arrangement for a cooking appliance airflow system. More specifically, there exists a need for an airflow sensor that maintains alignment and is capable of withstanding vibration and other abuses associated with shipping.
The present invention is directed to a cooling system airflow sensor provided in an oven. More specifically, the oven includes an oven cavity, a controller and a heat source for generating hot gases within the oven cavity. In addition, the oven includes a cooling system for preventing the oven gases maintained within the oven cavity from effecting the controller and, in addition, neighboring structure such as kitchen cabinetry and the like.
In accordance with a preferred form of the invention, the cooling system includes an air inlet and an air outlet separated by an air passage. Preferably, the air inlet is positioned along a control panel, with the air passage extending over the oven cavity. A cooling fan is arranged within the air passage for establishing a cooling airflow that is directed through the passage to various regions of the appliance and, ultimately expelled through the air outlet, preferably arranged in a rear portion of the appliance. More specifically, the cooling fan includes a drive shaft having secured thereto a multi-pole magnet. A Hall effect sensor is positioned in association with the multi-pole magnet for detecting a rotation of the drive shaft. The Hall effect sensor provides pulses to the controller that are translated into digital outputs used to calculate the speed of the fan.
In accordance with one aspect of the invention, if the controller determines that the cooling fan is being operated below a predetermined level, e.g. approximately 1000 RPM, the controller will assume that inadequate cooling is being provided to the appliance and terminate a current cooking operation. Once the cooking operation is terminated or cancelled, a corresponding fault code is generated by the controller for display to a user or service technician. In accordance with another aspect of the present invention, if the controller determines that the cooling fan is operating above a predetermined level, e.g., approximately 3000 RPM, the controller will assume that the fan has become detached from the drive shaft and the controller will again halt the current cooking operation, while generating and displaying a corresponding fault code.
Additional objects, features and advantages of the present invention will become more readily apparent from the following detailed description of a preferred embodiment when taken in conjunction with the drawings wherein like reference numerals refer to corresponding parts in the several views.